To help out his friend Edie Adams financially after her husband Ernie Kovacs's sudden death left her debt-ridden, star/co-producer Jack Lemmon not only insisted upon hiring her for this film, but further insisted that her part be expanded considerably from the original stage play to give her more work.
The red sports car Hogan drives is a 1962 Ford Cougar 406 concept car. It was introduced at the 1962 Chicago Auto Show.
According to movie magazines of the day, Natalie Wood, Ann-Margret, Stella Stevens, and Sandra Dee reportedly vied for the role played by Carol Lynley.
Gig Young originally announced to re-create his stage role on film, but the part went to Jack Lemmon instead.